The present disclosure relates to a mounting method for mounting electric components on a substrate.
In a mounting step for connecting electric components such as a semiconductor element or the like on the substrate, a compression bonding device in which the electric components are heated, while being pressed to the substrate with a pressing head. A reference numeral 101 of FIG. 14(a) denotes a prior art compression bonding device, and the compression bonding device 101 includes a base 126 and a pressing head 120.
As the pressing head 120, there are a pressing head having a pressing rubber fitted into a metallic frame, a pressing head having a pressing rubber bonded to a metallic plate with an adhesive, a pressing head in which a liquid rubber is flown in a metallic frame and cured therein, etc.
The pressing head having the pressing rubber 122 fitted into the head body 121 made of the metallic frame will be explained. The front face of the pressing rubber 122 is flush with that of the head body 121, or is projected outwardly beneath the front face of the head body 121. When the pressing head 120 is pressed onto an object 110 to be compression bonded, on the base 126, the surface of the pressing rubber 122 is in contact with the object 110 to be compression bonded.
The object 110 to be compression bonded includes a substrate 111 and electric components 116 and 118, which are placed on the substrate 111 and have different thicknesses. A step is formed on the substrate 111 due to a difference in thickness between the electric components 116 and 118.
The pressing rubber 122 is made of an elastic material deformable upon application of a force. The pressing rubber 122 is in first contact with the thickest electric component 116, and is deformed to be in contact from the thicker electric component 116 to the thinner electric component 118 successively, so that the thicker electric component 116 to the thinner electric component 118 are ultimately entirely pressed with the pressing rubber 122 through deformation.
Before the electric components 116, 118 are pressed by the compression bonding device 101, the electric components 116, 118 are aligned with the substrate 111, and terminals of the electric components 116, 118 are located immediately above those of the substrate 111 via an adhesive 115.
The surface of the base 126 is made substantially horizontal, and the substrate 111 is horizontally placed on that surface. When the electric components 116 and 118 are pressed by moving the pressing head 120 vertically downwardly, while the object 110 to be compression bonded is being heated, the electric components 116, 118 move down, pressing away the adhesive 115. Consequently, the terminals of the electric components 116, 118 are in contact with those of the substrate 111, and the electric components 116, 118 are electrically connected to the substrate 111 (FIG. 14(b)). In this way, the conventional compression bonding device 101 can simultaneously connect the electric components having different thicknesses with the single substrate.
Meanwhile, the pressing rubber 122 has the property that when it is deformed on pressing the electric components 116, 118, its peripheral portion swells as a reaction. Thus, the swelled portion of the pressing rubber 122 runs over a frame of the head body 121, and the front face of the pressing rubber 122 spreads horizontally.
FIG. 15 is a plan view showing a state in which the front face of the pressing rubber 122 spreads horizontally, and the pressing rubber 122 flows around the center C of the planar shape in radial directions. As compared with near the center C of the pressing rubber 122, the moving amount of the end portion is greater, so that the electric components 116, 118 to which the end portion of the pressing rubber 122 is pressed, move horizontally with the spreading of the pressing rubber 122, and the terminals of the electric components 116, 118 slip off from the positions immediately above those of the substrate 111.
When the electric components 116, 118 positionally slip, the terminals of the electric components 116, 118 are not in contact with those of the substrate 111, so that the reliability in connection between the electric components 116, 118 and the substrate 111 decreases.
In case that the electric components 116, 118 are to be mounted not only on one face of the substrate 111 but also on the opposite faces, the electric components 116, 118 need to be mounted face by face and in twice, which increases the time required for the mounting.
Furthermore, in case that the electric components 116, 118 are mounted on one face and then the electric components 116, 118 are mounted on the other face, since the surface on which the electric components 116, 118 have been already mounted is faced to the base 126, convex-concave portions need to be formed for the base 126 in conformity with the shapes of the electric components 116, 118 so that the mounted electric components 116, 118 may hardly be damaged with pressing pressure.
However, this method requires bases 126 to be remade every time when the type of electronic parts 116, 118 and substrates 111 or connecting positions of the electric components 116, 118 change.
Further, the electric components 116, 118 having been mounted on one face are heated and pressed again when the electric components 116, 118 are connected to the other face. Thus, electric components 116, 118 are sometimes damaged through repeated heating and pressing. The conventional device is disclosed in JPA 2002-359264 and JPA 2005-32952, for example.